Alex Pasculle, an 18-year-old senior, has been with Murrysville Medic One for five months. He said he has been working in emergency services since he was 14, and had been a certified EMT for about a year.

Pasculle knew something was off when he heard the fire alarm during homeroom period Wednesday morning.

"I went to go downstairs whenever someone told me not to go downstairs. That's whenever I saw somebody had been stabbed," he said.

Pascuelle had his first aid bag in his car, so he ran toward the exit. On his way out, he said he told the school resource officer, Murrysville police officer Wililam "Buzz" Yakshe, that there was an attacker in the building.

"I parked my car and ran up front to start triaging people," Pasculle said. "I started treating people outside. I didn't have tags or anything, so I just tried to remember who is who. I had gauze, so I would give someone gauze and have the person who was staying with them and tell them to hold it."

After taking off his shirt and giving it to a teacher to apply pressure on victims waiting outside, Pasculle was able to make his way inside the school to help more victims.

Pasculle said he noticed principals Sam King and Joan Mellon were sitting atop the suspect, while security officer John Resetar was hurt in his stomach area. Pasculle said he gave gauze to a maintenance worker and told him to hold it on Resetar's injury. At that point, the school nurse met up with Pasculle.

"There was actually so much blood that she fell getting up and then I fell getting up, too. When we were trying to get up, we couldn't even stand," Pasculle said.

After that, an anatomy teacher and Mellon told Pasculle he was needed to help critically wounded students.

"They were both like, 'Alex, we need you to room 114.' One fourteen, that's the number that's ingrained inside of my head because that's where the most serious people were," he said.

Pasculle said he created a makeshift dressing to keep one teen's deep abdomen wound from bleeding profusely until EMTs and police arrived on scene to take over.

"That directly saved lives. It directly saved lives, I know it did. From the bleeding, the amount of blood. Just simple wound pressure on something saved a life," Pasculle said. "For people who were on the edge of passing out, not passing out and being unconscious or not unconscious, just holding their hand and talking to them, keeping them alive, keep reminding them people are coming -- that saved the people."

Pasculle said staff members and teachers did a phenomenal job of staying inside the school to help the victims until emergency responders arrived.

"It really wasn't just me. It was a team effort. The faculty at our school, I mean every teacher in that hallway, stayed back. Every teacher stayed back. They could have all left. They put themselves in danger," Pasculle said. "It actually makes me feel pretty safe that I have people at my school who would put their life on the line, stay back and do whatever they could to help a student."

Murrysville police said the suspect, 16-year-old Alex Hribal, was subdued by a school resource officer and an assistant principal after allegedly wounding 21 students and a security guard. He is being held without bond, facing adult charges of attempted homicide and aggravated assault.

Refresh this page later for updates. Watch the full interview with Alex Pasculle on Pittsburgh's Action News 4 tonight at 5 p.m.

HE DOES BELIEVE HIS CLIENT AT THE AGE OF 16 COULD BE REHABILITATED. WE'RE ALSO HEARING ABOUT ANOTHER STUDENT HERO. AN EMT WHO RACED TO SAVE LIVES. PITTSBURGH ACTION NEWS 4 REPORTER ASHLIE TALKED WITH HIM. TALK ABOUT REMARKABLE COMPOSURE FOR SUCH A YOUNG PERSON. Reporter: HE'S WISE BEYOND HIS YEARS. WE'RE TALKING ABOUT ALEX PASCAL. HE'S CREDITING FACULTY, STAFF, FELLOW STUDENTS AND FIRST RESPONDERS FOR THEIR TEAM WORK AND FOR THEIR RELENTLESS PURSUIT TO STAY BY THE SIDES OF THESE VICTIMS AND MAKE SURE THEY'RE OKAY. THIS YOUNG MAN'S OWN DISREGARD FOR HIS OWN SAFETY LITERALLY LIKELY SAVED THE LIVES OF TWO OF HIS CLASSMATES. ALEX IS JUST 18. A FRANKLIN REGIONAL SENIOR AND EMT. HE RAN FROM THE SCHOOL TO GET HIS FIRST AID BACK AND RAN BACK TOWARD THE BUILDING TO HELP PEOPLE BEFORE HE EVEN KNEW IF THE ATTACKS WERE OVER. THE ONE PERSON ON THE GRASS I TOOK MY SHIRT OFF AND THREW MY SHIRT TO THE TEACHER AND SAID IF YOU NEED TO USE THIS, USE THIS. Reporter: AFTER HELPING WOUNDED VICTIMS ON THE LAWN HE RAN SBINTO THE BUILDING AND SAW THE PRINCIPAL HOLDING THE SUSPECT DOWN. HE RADIOS FOR HELP. HE NOTICED THE SECURITY GUARD WAS HURT. HE GAVE HIM GAUZE, WHICH A MAINTENANCE WORKER HELD ON HIM. I DIDN'T HAVE TAGS OR ANYTHING. I WOULD GIVE SOMEONE GAUZE AND HAVE THE PERSON STAYING WITH THEM AND TOLD THEM WHAT TO DO. I STARTED GOING DOWN THE HALL MAKING MY WAY WHILE THE PRINCIPAL WAS LIKE WE NEED YOU HERE. WE NEED YOU HERE. Reporter: THEN HE WAS CALLED BY TWO STAFFERS TO A ROOM WHERE TWO VICTIMS, INCLUDING A BOY WHO HE WAS EVISCERATED NEEDED HELP. HE MADE A MAKESHIFT DRESSING TO KEEP HIS ABDOMEN IN ATTACK. HE TENDED TO 14 OF THE 14 TOTAL VICTIMS LIKELY KEEPING TWO OF THEM ALIVE. PEOPLE ON THE EDGE OF PASSING OUT JUST HOLDING THEIR HAND AND TALKING TO THEM AND KEEPING THEM ALIVE AND REMINDING THEM THERE ARE PEOPLE COMING. THAT SAVED THE PEOPLE. Reporter: NOW, OUR INTERVIEW WAS EXTENSIVE. AT 6:00, HE WILL DESCRIBE WHY HE SAYS THE FIRST AID PROCESS WENT

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